Can Renal Cysts Develop Into Cancer?

Simple renal cysts are often found even in normal kidneys. In fact, they are so common that they are rarely considered as a disease. Certain lifestyle traits or genetics can be the cause of renal cysts occurring in adults as well as children, though no conclusive reasons have yet been confirmed for the occurrence of the same. Medical imaging technology such as ultrasound, X-ray, and CT scanning are being extensively used to discover these lesions.

In various surveys of people undergoing ultrasound for evaluation of non-kidney-related problems, generally 15% men and 7% women over the age of 50 were detected with renal cysts. Once the radiologic imaging of the cyst is obtained, the doctor can determine what further examination will be required.

There are basically two types of renal cysts, simple and complex.

• Simple cysts are usually round, have a thin outer wall, are filled with fluid and are rarely required to be treated.
• Complex cysts, however, can have thicker walls with solidified mass or can also be a collection of small cysts. These are definitely required to be examined further as they can be cancerous.

With the latest radiological approach to renal cysts, i.e. the Bosniak classification, observation of lesions is preferred to biopsy. Even though biopsies nowadays are largely non-intrusive, they are still recommended under very specific circumstances.

This classification uses a complicated algorithm of CT scan features like size, density and perfusion and places cystic renal masses into one of the five different categories. Categories I and II are generally simple cysts, not requiring further analysis. Still, an ultrasound is repeated at intervals of 6-12 months to ensure that the cyst is not growing. However, Bosniak category IIF cysts indicate complex cysts which are required to be observed. Lack of change with time indicates that the mass is benign, while any increase indicates the possibility of cancer. Through observation, one can prevent unnecessary surgeries.

It is mostly recommended that lesions falling under Bosniak III category should be immediately surgically removed as 40-50% have the possibility of becoming cancerous. However, close follow-up with magnetic resonance imaging can be used to avoid unnecessary surgeries as it is useful for characterizing the internal content of a cyst which may be is indeterminate even after the ultrasound and CT scan. Category IV lesions necessarily require surgical removal of the kidney, as nearly 85-100% of these are cancerous. More than 90% of those diagnosed with renal cancer which is confined to the kidney can hope to become disease-free within five years after diagnosis.

Thus, complex renal cysts have a higher possibility of developing into cancer if they are found to be malignant during the period of observation and steps should be taken for immediate removal.

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